1. Field of the Invention
The present invention relates to a rotary impacting apparatus, and more specifically to a rotary impacting apparatus suitable to such tasks as underground root cutting or plant cutting above the ground.
2. Description of the Related Arts
Generally, the impacting apparatus represented for instance by a concrete breaker utilizes expansive force of compressed air or a combination of a prime motor and a crank mechanism for forcibly reciprocating an impacting piston in the main body. When reciprocated, the impacting piston repetitively hits a reciprocating implement supported at an end portion of the main body in an axial direction.
Recently, however, a new type of impacting apparatus differing from the reciprocating type described hereinabove has been introduced. This type, called "rotary impacting apparatus", is developed for decreasing the reaction of the impact and increasing the impacting frequency. The basic constitution of the rotary impacting apparatus is disclosed, for instance, in the U.S. Pat. No. 5,002,134.
The apparatus disclosed in the above United States Patent comprises a housing in which a rotor is driven by a drive source, and an impact member of a predetermined mass loosely and eccentrically held by the rotor. When the rotor rotates, the impact member repeatedly hits the top end of a reciprocative implement slidably supported by the housing, thereby driving the reciprocative implement.
When using the rotary impacting apparatus, the operator supports the apparatus by holding a grip portion of a handle with the forward end of the reciprocative implement held against the ground for instance. The drive source is then turned on to rotate the rotor for causing the impact member to repeatedly hit the top end of the reciprocating implement, thereby driving the reciprocative implement into the ground. At the lower end of the reciprocative implement, there is mounted or integrally formed a suitably shaped tool such as blade or shovel depending on the applications.
One of such applications is the removal of a tree from the ground for shipment. For reliably performing the removal which is followed by subsequent re-planting and growing thereof, the entire root system of the tree must be carefully trimmed about a year before the planned shipment. This root trimming procedure must be performed thoroughly so that no root branches are left untrimmed, and for this purpose it is necessary to drive the tip of the reciprocative implement down to 50 cm underground.
Another application is the harvesting of sugarcane. Sugarcane has a high sugar content in its base portion buried in the ground. Traditionally, the cutting or harvesting must be done entirely by hand using a special tool called a pick.
Still another application which invloves laborious plant cutting is the crop yielding high above the ground. Specifically, as shown in FIG. 16, harvesting of coconuts Ya is performed by operating a long pusher rod from the ground. Such coconut yielding is under an increasing demand recently for palm oil production.
As will be understood from the FIG. 16, some coconuts Ya grow behind thickly growing palm leaves. Thus, these coconuts Ya can only be harvested after the blocking palm leaves are cut away by a cutting blade 50x mounted at the forward end of the pusher rod 50.
The rotary impacting apparatus disclosed in the above United Sates Patent may be used for the root trimming or coconut harvesting. However, with this rotary impacting apparatus the impact member in the housing hits the reciprocative implement only in the advancing direction.
On the other hand when the reciprocative implement is pulled out of the ground, a great friction may act on the reciprocative implement due to the root system or a great ground pressure. As a result, the impacting apparatus cannot be pulled out by an ordinary pulling force exerted on the handle of the apparatus, making the job very difficult and inefficient.
This problem is particularly serious when the rotary impacting apparatus is used for the root trimming process. Specifically, the root system may develops so randomly beneath the tree trunk that once the cutting blade is driven into the ground and held firmly by the root system, it becomes extremely difficult to pull the blade. In addition, when the reciprocative implement is driven to a depth of 50 cm as required for the root trimming process, the ground pressure becomes too large for an ordinary operator to pull the blade out of the ground.
On the other hand when the coconut Ya is harvested (see FIG. 17), the cutting blade 50x is driven into the base portion Yc of the palm leaf Yb. However, it is usually difficult for a single driving action to make a complete cut, and the cutting blade 50x driven halfway into the base portion Yc of the palm leave Ya receives a force W corresponding substantially to the entire weight of the palm leaf. Thus, even if the cutting blade 50x is replaced by the reciprocative implement of the rotary impacting apparatus, there is still a problem of difficulty in pulling the reciprocative implement off the leaf base portion.